1. Field of the Invention
The invention concerns the use of a butt connection between components, in which straps arranged along a butt joint bridge over the butt joint and are respectively fixed with their ends directly to one of the components to be connected with a small longitudinal spacing from the butt joint.
2. Description of Related Art
Similarly to aircraft propellers, the rotors of wind power installations have rotor blades comprising a load-bearing spar or beam member—in most cases with an upper and a lower flange—and a hollow profile member which determines the aerodynamic properties of the rotor. Nowadays the hollow profile members generally comprise composite materials, namely glass or carbon fibers with polyester or epoxy resins as binders. What has become the usual practice is producing the rotor blade hollow profile members (whose cross-section generally changes over the length thereof) in the form of two longitudinally divided half-shell portions which are assembled to the spar to form the finished blade.
With the increasing power of modern wind power installations, the rotors thereof are also becoming larger in diameter, which requires the production of correspondingly longer rotor blades. If the production of such long rotor blades, that is to say the half-shell portions required for same, in one piece, is already not without its problems (inter alia because of the correspondingly large factory building), transportation which is then required to the location at which the wind power installation is erected represents a serious obstacle.
DE 29 21 152 A1 discloses a transversely divided rotor blade whose hollow profile member parts are connected by means of the butt connection described in the opening part of this specification. In that arrangement the ends of the profile member parts are engaged by tensile anchors, between which the clamping elements in the form of steel cables or steel plates are tensioned, which pass through in the interior of the profile member parts over the blade length, possibly also through additional intermediate anchors. That arrangement gives rise to problems insofar as the specific change in length of the clamping elements under the effect of fluctuations in temperature and/or centrifugal forces, which depends on the coefficient of expansion and the modulus of elasticity of the material used, has the effect, because of the great length of the clamping elements, of giving rise to considerable absolute changes in length which cannot be accommodated by the prestressing of the clamping elements and which result in loosening of the butt connection.
U.S. Pat. No. 3,310,327 A1 also discloses the butt connection described in the opening part of this specification, which serves for connecting prefabricated component parts of buildings or the like. Fixed to the ends of the straps are bolts which engage over their entire length into the full material of the component parts.